In the real space, orthogonal transformation keeps metric not changing, and transform matrix in the orthogonal transformation is orthogonal matrix.So it is very important to research transform matrix.

• 在实空间中正交变换保持度量不变，而正交变换中对应的变换矩阵就是正交矩阵，所以对正交矩阵的研究就显得格外重要。